- #1

Kaguro

- 221

- 57

- Homework Statement
- Consider a cube ABCDEFGH of volume V containing N molecules each of mass m with

uniform density n =N/V . Suppose this system is equivalent to a system of M non-interacting gases such that molecules of the i th gas are N_i = n_i*V in number, each with an

identical y -component of velocity v_i . What is the pressure P on the surface , ABCD of

area A, perpendicular to the positive y axis?

- Relevant Equations
- PV=NkT, where N is total number of molecules

Vrms=sqrt(1.5kT)

I wrote energy of each molecule is ##\frac{1}{2}mv_{rms}^2 \Rightarrow E/3 = \frac{1}{2}mv_i^2##. So total energy of each type of gas is

##E_i = N_i\frac{3}{2}mv_i^2## Now, PV=E. So total Pressure = Sum of energies/volume

##P=\frac{\frac{3m}{2}\sum_i N_i v_i^2}{V} =\frac{3m}{2} \sum_i n_i v_i^2 ##

But answer given is just ##m \sum_i n_i v_i^2 ##

Help.

##E_i = N_i\frac{3}{2}mv_i^2## Now, PV=E. So total Pressure = Sum of energies/volume

##P=\frac{\frac{3m}{2}\sum_i N_i v_i^2}{V} =\frac{3m}{2} \sum_i n_i v_i^2 ##

But answer given is just ##m \sum_i n_i v_i^2 ##

Help.